[ostree] Add 'ostree reset' command to undo a bad commit

[Stefan Walter <stefw src gnome org>]

commit f9b2c45fc0c299b288c84ea84e78b5406807a4c9
Author: Stef Walter <stefw redhat com>
Date:   Wed Aug 14 12:42:13 2013 +0200

    Add 'ostree reset' command to undo a bad commit
    
    Accepts the following arguments: ref checksum
    
    Checks that the checksum is a parent of the ref before rewriting
    the ref.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=705979

 Makefile-ostree.am            |    1 +
 src/ostree/main.c             |    1 +
 src/ostree/ot-builtin-reset.c |  134 +++++++++++++++++++++++++++++++++++++++++
 src/ostree/ot-builtins.h      |    1 +
 tests/test-basic.sh           |   12 ++++-
 5 files changed, 148 insertions(+), 1 deletions(-)
---
diff --git a/Makefile-ostree.am b/Makefile-ostree.am
index ccfd374..58aa676 100644
--- a/Makefile-ostree.am
+++ b/Makefile-ostree.am
@@ -36,6 +36,7 @@ ostree_SOURCES = src/ostree/main.c \
        src/ostree/ot-builtin-prune.c \
        src/ostree/ot-builtin-refs.c \
        src/ostree/ot-builtin-remote.c \
+       src/ostree/ot-builtin-reset.c \
        src/ostree/ot-builtin-rev-parse.c \
        src/ostree/ot-builtin-show.c \
        src/ostree/ot-builtin-write-refs.c \
diff --git a/src/ostree/main.c b/src/ostree/main.c
index 1542095..ae0e3ce 100644
--- a/src/ostree/main.c
+++ b/src/ostree/main.c
@@ -43,6 +43,7 @@ static OstreeCommand commands[] = {
   { "log", ostree_builtin_log, 0 },
   { "ls", ostree_builtin_ls, 0 },
   { "refs", ostree_builtin_refs, 0 },
+  { "reset", ostree_builtin_reset, 0 },
   { "prune", ostree_builtin_prune, 0 },
 #ifdef HAVE_LIBSOUP 
   { "pull", ostree_builtin_pull, 0 },
diff --git a/src/ostree/ot-builtin-reset.c b/src/ostree/ot-builtin-reset.c
new file mode 100644
index 0000000..44e0450
--- /dev/null
+++ b/src/ostree/ot-builtin-reset.c
@@ -0,0 +1,134 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2013 Stef Walter <stefw redhat com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ * Author: Stef Walter <stefw redhat com>
+ */
+
+#include "config.h"
+
+#include "ot-builtins.h"
+#include "ostree.h"
+#include "otutil.h"
+
+static GOptionEntry options[] = {
+  { NULL }
+};
+
+static gchar *
+find_current_ref (OstreeRepo   *repo,
+                  const gchar  *ref,
+                  GCancellable *cancellable,
+                  GError      **error)
+{
+  gs_unref_hashtable GHashTable *refs = NULL;
+  gchar *ret;
+
+  if (!ostree_repo_list_refs (repo, NULL, &refs, cancellable, error))
+    return NULL;
+  ret = g_strdup (g_hash_table_lookup (refs, ref));
+  if (ret == NULL)
+    g_set_error (error, G_IO_ERROR, G_IO_ERROR, "The ref was not found: %s", ref);
+
+  return ret;
+}
+
+static gboolean
+check_revision_is_parent (OstreeRepo   *repo,
+                          const char   *descendant,
+                          const char   *ancestor,
+                          GCancellable *cancellable,
+                          GError      **error)
+{
+  gs_free char *parent = NULL;
+  gs_unref_variant GVariant *variant = NULL;
+  gboolean ret = FALSE;
+
+  if (!ostree_repo_load_variant (repo, OSTREE_OBJECT_TYPE_COMMIT,
+                                 descendant, &variant, error))
+    goto out;
+
+  parent = ostree_commit_get_parent (variant);
+  if (!parent)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                   "The ref does not have this commit as an ancestor: %s", ancestor);
+      goto out;
+    }
+
+  if (!g_str_equal (parent, ancestor) &&
+      !check_revision_is_parent (repo, parent, ancestor, cancellable, error))
+    goto out;
+
+  ret = TRUE;
+out:
+  return ret;
+}
+
+gboolean
+ostree_builtin_reset (int           argc,
+                      char        **argv,
+                      GFile        *repo_path,
+                      GCancellable *cancellable,
+                      GError      **error)
+{
+  GOptionContext *context;
+  gboolean ret = FALSE;
+  const char *ref;
+  const char *target = NULL;
+  gs_unref_object OstreeRepo *repo = NULL;
+  gs_free gchar *current = NULL;
+  gs_free gchar *checksum = NULL;
+
+  context = g_option_context_new ("[ARG] - Reset a ref to a previous commit");
+  g_option_context_add_main_entries (context, options, NULL);
+
+  if (!g_option_context_parse (context, &argc, &argv, error))
+    goto out;
+
+  repo = ostree_repo_new (repo_path);
+  if (!ostree_repo_check (repo, error))
+    goto out;
+
+  if (argc <= 2)
+    {
+      ot_util_usage_error (context, "A ref and commit argument is required", error);
+      goto out;
+    }
+  ref = argv[1];
+  target = argv[2];
+
+  if (!ostree_repo_resolve_rev (repo, target, FALSE, &checksum, error))
+    goto out;
+
+  current = find_current_ref (repo, ref, cancellable, error);
+  if (current == NULL)
+    goto out;
+
+  if (!check_revision_is_parent (repo, current, checksum, cancellable, error))
+    goto out;
+
+  if (!ostree_repo_write_ref (repo, NULL, ref, checksum, error))
+     goto out;
+
+  ret = TRUE;
+ out:
+  if (context)
+    g_option_context_free (context);
+  return ret;
+}
diff --git a/src/ostree/ot-builtins.h b/src/ostree/ot-builtins.h
index 69af373..4fbb4c1 100644
--- a/src/ostree/ot-builtins.h
+++ b/src/ostree/ot-builtins.h
@@ -40,6 +40,7 @@ gboolean ostree_builtin_pull_local (int argc, char **argv, GFile *repo_path, GCa
 gboolean ostree_builtin_ls (int argc, char **argv, GFile *repo_path, GCancellable *cancellable, GError 
**error);
 gboolean ostree_builtin_prune (int argc, char **argv, GFile *repo_path, GCancellable *cancellable, GError 
**error);
 gboolean ostree_builtin_refs (int argc, char **argv, GFile *repo_path, GCancellable *cancellable, GError 
**error);
+gboolean ostree_builtin_reset (int argc, char **argv, GFile *repo_path, GCancellable *cancellable, GError 
**error);
 gboolean ostree_builtin_fsck (int argc, char **argv, GFile *repo_path, GCancellable *cancellable, GError 
**error);
 gboolean ostree_builtin_show (int argc, char **argv, GFile *repo_path, GCancellable *cancellable, GError 
**error);
 gboolean ostree_builtin_rev_parse (int argc, char **argv, GFile *repo_path, GCancellable *cancellable, 
GError **error);
diff --git a/tests/test-basic.sh b/tests/test-basic.sh
index 154a93d..de372bd 100755
--- a/tests/test-basic.sh
+++ b/tests/test-basic.sh
@@ -19,7 +19,7 @@
 
 set -e
 
-echo "1..38"
+echo "1..39"
 
 . $(dirname $0)/libtest.sh
 
@@ -265,3 +265,13 @@ assert_file_has_content log-output "commit $checksum1"
 assert_file_has_content log-output "Second commit"
 assert_file_has_content log-output "commit $checksum2"
 echo "ok log output"
+
+cd ${test_tmpdir}
+checksum1=$($OSTREE commit -b test6 -s "First commit")
+checksum2=$($OSTREE commit -b test6 -s "Second commit")
+$OSTREE show test6 > show-output
+assert_file_has_content show-output "commit $checksum2"
+$OSTREE reset test6 $checksum1
+$OSTREE show test6 > show-output
+assert_file_has_content show-output "commit $checksum1"
+echo "ok basic reset"